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Accepted
Sergey Kuznetsov
Asked:2020-06-29 13:21:53 +0000 UTC2020-06-29 13:21:53 +0000 UTC

从原点和线段找到线的交点。matpoltib

  • 772

给定一条由方程 y=kx 给出的直线和一段 PB1。需要找到这些线的交点的坐标，并将其绘制在图形上。

import numpy as np
import matplotlib.pyplot as plt

p = (input("choose point P on axis OX: "))
print(p)

k = np.random.rand(1)
X = np.arange(-50, 50, 1)
Y = k*X
# arbitrary line across O
plt.plot(X,Y)

plt.plot(0,0)
plt.scatter(0.0, 0.0, color='white', marker='o')
plt.text(0.0, 0.0, "O", horizontalalignment="center")

plt.plot(p,0)
plt.scatter(p, 0.0, color='green', marker='o')
plt.text(p, 0.5, "P", horizontalalignment="center")

xmin= -50
xmax= 50
ymin= -50
ymax= 50
ax = plt.gca()
ax = plt.gca()
ax.set_xlim([xmin,xmax])
ax.set_ylim([ymin,ymax])
ax.spines['left'].set_position('center')
ax.spines['bottom'].set_position('center')
ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)

#create random point B1

b1 = 14
plt.plot(0.0,b1)
plt.scatter(0.0, b1, color='blue', marker='o')
plt.text(0.5, b1, "B1", horizontalalignment="center")

#create PB1
plt.plot([0,p],[b1,0])

plt.show()

在此处输入图像描述

matplotlib

2 个回答

  1. Best Answer

    使用链接提供的答案：https ://stackoverflow.com/questions/28766692/intersection-of-two-graphs-in-python-find-the-x-value 找到线交点的实现是：

    import numpy as np
import matplotlib.pyplot as plt

p = (input("choose point P on axis OX: "))
print(p)

k = np.random.rand(1)
X = np.arange(-50, 50, 0.05)
Y = k*X
# arbitrary line across O
plt.plot(X,Y)

plt.plot(0,0)
plt.scatter(0.0, 0.0, color='white', marker='o')
plt.text(0.0, 0.0, "O", horizontalalignment="center")

plt.plot(p,0)
plt.scatter(p, 0, color='green', marker='o')
plt.text(p, 0.3, "P", horizontalalignment="center")

xmin= -10
xmax= 10
ymin= -10
ymax= 10
ax = plt.gca()
ax = plt.gca()
ax.set_xlim([xmin,xmax])
ax.set_ylim([ymin,ymax])
ax.spines['left'].set_position('center')
ax.spines['bottom'].set_position('center')
ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)

#create point B1
b1 = 9
plt.plot(0.0,b1)
plt.scatter(0.0, b1, color='blue', marker='o')
plt.text(0.5, b1, "B1", horizontalalignment="center")

# #create PB1
l = -b1*X/p + b1
plt.plot(X,l)

# found point across O and B1P (search S)
idx = np.argwhere(np.diff(np.sign(Y - l))).flatten()
plt.plot(X[idx], Y[idx], 'ro')
plt.text(X[idx]+0.1, Y[idx], "S", horizontalalignment="center")
plt.show()

    结果显示为： 在此处输入图像描述

    • 1

  2. 在这种简单的情况下，找到一个点——据我所知，某种搜索——并不是很合理。解方程就足够了：

    y = b1 - x * b1 / p = k * x
x * (k + b1 / p) = b1
x = b1 * p / (k * p + b1) //вот и результат

    在这种情况下，是这样的：

    x = 9 * 7 / (0.5 * 7 + 9) = 5.04
    • 1

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